I've been working on Amy Butler's Weekender Bag in my spare time for the last few weeks. Last night, I was ready - or so I thought - to put in the zipper. As I was trying to line everything up, I noticed I bought the wrong type of zipper. I did a bit of internet research, but can't seem to find a 30" non-separating/closed bottom zipper. To those oof you who have made this bag, do you know where I can find the right zipper?